Soooo use the natural projection mapping and show that the kernel equals $B_1 \oplus .... \oplus B_k$? And that it's an epimorphism? Can somebody help me with the details? What are the main differences to this as to what proving it for rings and ideals? Nothing I suppose since Ideals are R-Modules... anyway yeah I just wanted to post this here because I figured one of you smarty pants would have something useful to say about it. Thanks!